Observations

Description

Valves are lanceolate with rostrate to subcapitate apices. The axial area is narrow. The central area is elliptic and slightly wider than the axial area. The raphe is filiform and somewhat sinuous, with inflated and relatively distant proximal raphe ends. Striae are parallel in the middle of the valve, becoming weakly radiate and then convergent near the apices. One or more striae in the central area are slightly shorter than adjacent striae. Areolae are distinct in LM and number a constant 28 in 10 µm. Valves with a Heribaudii stage were also present in the population observed. Craticula, however, were not observed.

Original Description

Original Description

Valves lanceolate with rostrate to subcapitate apices. Valve length 78–105 μm; valve width 18.0–19.3 μm. Axial area narrow, flaring somewhat to merge with an elliptic and slightly wider central area. Raphe filiform and somewhat sinuous with inflated and relatively distant proximal ends that are bent to the same side. Striae parallel in the middle, becoming weakly radiate and then convergent near the apices, 14 in 10 μm at valve center, 17 in 10 μm at the apices. One or more striae in the central area slightly shorter than adjacent striae. Areolae 28 in 10 μm. “Heribaudii” valves present with more strongly radiate striae and lower stria density; craticula valves not observed.

Original Images

Cite This Page: Bahls, L. (2012). Craticula johnstoniae. In Diatoms of the United States. Retrieved December 09, 2016, from http://westerndiatoms.colorado.edu/taxa/species/craticula_johnstoniae

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID:

Autecology Discussion

Craticula johnstoniae evidently tolerates a wide range in water quality. It has been collected from a circumneutral pond (pH 6.98) with low specific conductance (46 µS/cm) and from an alkaline pond (pH 8.1-11.1) with moderate specific conductance (302-313 µS/cm). At these locations it was found in association with Craticula cuspidata, C. acidoclinata, and C. sardiniana